Hi @matthewford thanks for reaching out.
This component is not currently being worked on. The GOV.UK Publishing attachment component however could be a starting point.
If you're interested in what components and patterns the GOV.UK Design System team are currently working on, have a look at the backlog board that shows all the things as they were prioritised by the Design System Working Group.
If you do get any user research findings from testing download links it'd be great if you could post them here